定义一个Matrix类，实现矩阵的加法和乘法

 #include<iostream>
 using namespace std;

 class Matrix
 {
     int row;//矩阵的行
     int col;//矩阵的列
     int **a;//保存二维数组的元素
 public:
     Matrix();//默认构造函数
     Matrix(int r, int c);
     Matrix(const Matrix &is);//拷贝构造函数
     void Set();//输入矩阵元素
     void Madd(const Matrix &is);//矩阵加
     Matrix Mmul(const Matrix &is);//矩阵乘
     void display();//显示矩阵元素
 };

 Matrix::Matrix(int r, int c)
 {
     row = r;
     col = c;
     a = (int **)malloc(sizeof(int*)*row);
     for (int r = ; r < row; r++)
     {
         *(a + r) = (int*)malloc(sizeof(int)*col);
     }
 }

 Matrix::Matrix(const Matrix & is)
 {//拷贝构造函数
     row = is.row;
     col = is.col;
     a = new int*[row];
     for (int i = ; i < row; i++)
     {
         a[i] = new int[col];
     }
     a = is.a;
 }

 void Matrix::Set()
 {
     printf("请输入数：\n");
     for (int i = ; i < row; i++)
         for (int j = ; j < col; j++)
             cin >> a[i][j];
 }

 void Matrix::Madd(const Matrix & is)
 {
     if (row != is.row || col != is.col)//判断两矩阵是否符合相加条件
     {
         cout << "相加的矩阵必须行和列一致";
     }
     else
     {
         for (int i = ; i < row; i++)
         {
             for (int j = ; j < col; j++)
             {
                 a[i][j] += is.a[i][j];
             }
         }
     }
 }

 Matrix Matrix::Mmul(const Matrix & is)
 {
     Matrix M3(this->row, is.col);
     if (this->col != is.row)//判断是否符合相乘条件
     {
         cout << "不符合两矩阵相乘的条件";
     }
     else
     {
         for (int i = ; i < M3.row; i++)
         {
             for (int j = ; j < M3.col; j++)
             {
                 M3.a[i][j] = ;
                 for (int n = ; n < is.row; n++)
                 {
                     M3.a[i][j] += this->a[i][n] * is.a[n][j];
                 }
             }
         }
     }
     return M3;
 }

 void Matrix::display()
 {//输出矩阵
     for (int i = ; i < row; i++)
     {
         for (int j = ; j < col; j++)
         {
             cout << a[i][j] << " ";
         }
         cout << endl;
     }
     cout << endl;
 }

 int main()
 {
     Matrix m1(, );
     m1.Set();
     m1.display();
     Matrix m2(, );
     m2.Set();
     m2.display();
     Matrix m3(, );
     m3.Set();
     m3.display();
     cout << "m1+m2=" << endl;
     m1.Madd(m2);
     m1.display();
     Matrix m4(m1.Mmul(m3));
     cout << "m1*m3=" << endl;
     m4.display();
     system("pause");
     return ;
 }

运行结果：